This invention relates to an apparatus for and method of treating substrate such as semiconductor wafer and glass substrate for liquid crystal display by applying a treatment liquid to the substrate, e.g., by means of spraying.
A variety of substrate treating apparatuses have been manufactured, for example, cleaning apparatus, developing apparatus, etching apparatus, and resist-removing apparatus. Generally, such substrate treating apparatus includes a treatment section for applying treatment liquid to a substrate, a tank for storing the treatment liquid, and a pump for flowing the treatment liquid from the tank to the treatment section. A plurality of substrates are successively transferred in the treatment section, and transferred out to next section after being treated with the treatment liquid supplied by a liquid supplier, e.g., spraying device, provided in the treatment section. The treatment liquid applied to a substrate is reflowed into the tank. The restored treatment liquid is flowed again to the liquid supplier of the treatment section by the pump. In this way, the treatment liquid is used in a circulating manner to treat substrate.
In such substrate treating apparatuses, many bubbles are generated in the treatment liquid because of the spraying of the treatment liquid towards the substrate and of falling impact of the treatment liquid from the substrate. Generated bubbles are carried to the tank and then dispersed in the treatment liquid stored in the tank. The treatment liquid containing bubbles is flowed to the treatment liquid supplier, and finally applied to a substrate.
If treatment liquid containing bubbles is applied to a substrate, bubbles deposit on a front surface of the substrate, thereby deteriorating a uniform treatment of the front surface of the substrate. Further, the presence of bubbles in the tank prevents an efficient function of the pump, leading to an unstable flow of treatment liquid. Furthermore, treatment liquid is subject to acidification due to an increased contact area between the treatment liquid and the air caused by the presence of bubbles. This accelerates deterioration of the treatment liquid. Accordingly, it is essential to suppress the generation of bubbles in treatment liquid in such substrate treating apparatuses.
In view of these problems, a variety of ways have been proposed to suppress the generation of bubbles in treatment liquid. For example, there has been proposed use of a spraying device whose spray holes are formed into such a shape that bubbles are unlikely to generate. Also, a slanted plate is provided below a substrate in a treatment section. In this construction, treatment liquid falling down from the substrate is received by this slanted plate to decrease a falling impact of the treatment liquid and prevent the treatment liquid from becoming turbulent. Also, there has been proposed addition of antifoaming agent to treatment liquid to make the treatment liquid less subject to bubbling. Further, there has been proposed use of a treatment liquid supplier having no spraying device.
However, these conventional bubble suppressing ways cannot completely prevent bubbles from generating and increasing over time. Particularly in the case that a spraying device is used as treatment liquid supplier, the generation of bubbles is so considerable that a system for circulating the treatment liquid is clogged by bubbles within a short period of time even if one of the above bubble suppressing ways is adopted.
Also, the addition of antifoaming agent has a likelihood of adversely affecting the treatment of substrate depending upon components of antifoaming agent.